Disease relevance of lytA

• A 2.9-kilobase Acc I fragment of the DNA of the pneumococcal bacteriophage Cp-1, containing the cpl gene, hybridizes with the lytA gene encoding the pneumococcal amidase [1].
• To some extent the tcp phenotype is reminiscent of iap in Listeria, lytA in Streptococcus pneumoniae and lyt in Bacillus subtilis, all of which are considered to represent murein hydrolase defects [2].
• The lytA gene encoding the autolysin of Streptococcus pneumoniae may be a virulence determinant [3].
• Although the exact function and regulation of the vex123-pep27-vncRS locus remains to be determined, several factors influence the autolysis behavior of S. pneumoniae, including the bacterial capsule, erythromycin, and the lytA and vex3 gene products [4].
• The pneumococcal lytA gene coding for the major autolysin (amidase) can be expressed in Streptococcus pneumoniae and Escherichia coli using unchanged promoter and termination signals [5].

High impact information on lytA

• The presence of genes affecting survival without changing growth sensitivity to antibiotics (vncS, lytA, hipAB, sulA, and mar) indicates that bacteria are able to control their fate [6].
• The 3' regions of the cpl and lytA coding sequences show considerable nucleotide sequence homology and the carboxyl-terminal domains of the deduced amino acid sequences of these lysins are quite similar: 73 of the carboxyl-terminal 142 amino acid residues are identical, and of the 69 substitutions, 55 are conservative [1].
• Two novel chimeric pneumococcal cell wall lytic enzymes, named LC7 and CL7, have been constructed by in vitro recombination of the lytA gene encoding the major autolysin (LYTA amidase) of Streptococcus pneumoniae, a choline-dependent enzyme, and the cpl7 gene encoding the CPL7 lysozyme of phage Cp-7, a choline-independent enzyme [7].
• Our results confirmed and extended previous findings by showing that competence-induced aggregation is abolished in a lytA-lytC double mutant, and absolutely requires CbpD and its N-terminal CHAP amidase domain [8].
• Mutagenesis of either nanA or lytA did not result in an additional attenuation of virulence in the ply deletion background [9].

Chemical compound and disease context of lytA

• The lytA gene and the DNA region located downstream of this gene are not involved in the formation of the type 3 capsular polysaccharide of Streptococcus pneumoniae [10].
• All these genes were expressed in E. coli under the control of either the lytP promoter of the lytA gene, which codes for the major pneumococcal autolysin, or the promoter of the tetracycline-resistance gene (tetP) [11].

Biological context of lytA

• Genetic diversity within lytA is limited, especially compared to the high levels of diversity seen in other pneumococcal virulence factor genes, although small blocks generating mosaic structure were identified [12].
• Allelic diversity of lytA in an extensive collection of clinical isolates was assessed by restriction fragment length polymorphism and confirmatory sequencing studies [12].
• Plasmids containing modifications at the 3' end of the lytA gene encoding the pneumococcal amidase were constructed by DNA recombinant techniques [13].
• The nucleotide sequences of the lytA gene from 29 pneumococcal isolates of various serotypes and 22 additional streptococci of the mitis group (including two Streptococcus pseudopneumoniae strains) have been compared and found to correspond to 19 typical (927-bp-long) and 20 atypical (921-bp-long) alleles [14].
• Pulsed-field gel electrophoresis of SmaI-restricted chromosomal DNA and Southern hybridization with the lytA DNA probe and probes specific for antibiotic resistance genes were used to characterize pneumococcal isolates [15].

Anatomical context of lytA

• The lytA-positive, ply-positive, spn9802-positive and spn9828-positive group was found frequently in saliva from healthy children, and in saliva and sputum from patients with pneumonia [16].

Associations of lytA with chemical compounds

• Genomic DNA of S. pneumoniae hybridised with a probe consisting of an internal fragment of the choline kinase gene of Saccharomyces cerevisiae and one consisting of the choline binding domain of lytA [17].

Other interactions of lytA

• Mutagenesis of either the ply, lytA, or pspA gene in S. pneumoniae D39 significantly reduced virulence, relative to that of the wild-type strain, indicating that the respective gene products contribute to pathogenesis [9].
• Three PCR techniques (amplification of the psaA, ply, and lytA genes) and a commercial kit (AccuProbe [GenProbe, San Diego, Calif.], based on hybridization with the 16S rRNA gene), all four of which claimed to be specific for Streptococcus pneumoniae, were used to identify 49 alpha-hemolytic streptococcal isolates suspected of being pneumococci [18].
• The lytA gene has a rather long (240-bp) leader sequence with a high A + T content (70%) that contrasts with the very short (2-bp) untranslated region of the polA gene [López et al., J. Biol. Chem. 264 (1989) 4255-4263], the unique pneumococcal transcription unit that had been characterized so far [5].
• These results also indicate that it may be possible to identify PSSP and penicillin-resistant S. pneumoniae by applying PCR using a combination of primers to detect the susceptible pbp2b gene, resistant pbp2b gene mutations, and the lytA gene [19].

Analytical, diagnostic and therapeutic context of lytA

• Chimeric genes were constructed by site-directed mutagenesis: a unique SnaBI restriction site in the cpl1 gene, coding for the phage lysozyme, was introduced at a location equivalent to the SnaBI site present in the lytA gene, which codes for the pneumococcal amidase [20].
• The presence in these signatures of distinctive restriction sites (namely, SnaBI, XmnI, and BsaAI) allowed the development of a simple, reliable, and fast method that combines PCR amplification of the lytA gene, digestion with BsaAI, and separation of the products by agarose gel electrophoresis [14].
• Sequence analysis of the lytA gene revealed that the Opt(s) streptococci carried lytA alleles characteristic of those present in nonpneumococcal streptococci of the mitis group [21].
• A sequence alignment showed that the main difference between typical and atypical lytA alleles resided in 102 nucleotide positions (including the 6 bp absent from atypical alleles) [14].
• Strains were confirmed to be pneumococci on the basis of bile solubility, and PCR detection or Southern blotting hybridization of lytA and psaA, genes ubiquitous in this species [22].

References